Politicians have been warned that investment in the North Sea could be hampered if both sides of the independence debate continue to use the oil and gas industry as a political football.

The latest survey of oil and gas firms by Aberdeen & Grampian Chamber of Commerce found 38% of respondents indicating the independence referendum in September 2014 and its possible consequences as a factor in future plans.

That compares with a total of 32% who said the referendum was a factor over the period of the two previous six-monthly surveys published by the chamber.

Ironically, the warning comes as firms said in the same survey they expect to increase activity in UK waters and boost investment in developing new assets.

Based on current trends, the chamber's chief executive, Robert Collier, expects the referendum to become a factor for more industry players as the date of the vote approaches.

"We would expect this to increase should the Yes and Better Together campaigns continue to use oil and gas as a political football in the independence debate," he said.

The findings of the latest survey indicate there is still widespread uncertainty about what Scotland becoming independent could mean for the industry.

The survey said: "The majority indicated it was difficult to form an opinion in the absence of details as to any regulatory, taxation and policy changes, or to the arrangements for transferring any current arrangements, and as such expressed some concerns as to the potentially negative effects of the current uncertainties on business planning."

The survey found "slightly more than 30%" thought it would lead to more complications, especially for companies that operated in both England and Scotland and both the northern and southern North Sea. Around 10% thought the importance of the sector would require any government to reach an acceptable compromise on regulatory and tax policies.

The chamber says the twice-yearly survey provides an authoritative view of what is happening in a sector which plays a vital economic role in the north-east, in Scotland and the UK as a whole.

Conducted by the Fraser of Allander Institute at Strathclyde University, the survey draws upon detailed responses from a wide range of oil and gas producers and services companies.

The survey findings suggest the North Sea industry is booming.

Some 80% of oil and gas firms expect to increase investment in new facilities in 2013/14. However, the chamber warned: "There remains a question mark over the longevity and sustainability of the current high level of investment and activity beyond 2015/16. The region will have to work hard to maintain current success."

Energy Minister Fergus Ewing welcomed the survey's findings, saying: "This is a hugely positive report on the future of Scotland's North Sea oil and gas industry - There are an estimated 24 billion barrels of oil still to be recovered, with a potential wholesale value of up to £1.5 trillion – and with some estimates suggesting it could be substantially higher still."

Scottish Liberal Democrat leader Willie Rennie said Mr Ewing was playing "wild guessing games" about the prospects for oil.